This invention relates to the development of improved penetration and expansion bullets for law enforcement and personal defense use. It is particularly related to the development of a hollow-point bullet intended for law enforcement use and personal defense and which exhibits optimum penetration and more reliable and consistent expansion than prior art hollow-point bullets, while maintaining near 100% weight retention, when fired through barrier materials such as wall board, plywood, sheet metal and heavy clothing before entering its primary target.
Any material encountered by the bullet before it reaches its intended target is referred to as a barrier material. Heavy clothing, sheet steel, wall board (gypsum board), plywood, or automobile glass would all be considered to constitute barrier materials because they tend to plug the cavity of the hollow-point so as to preclude the collection of viscous materials therein. Such viscous materials induce expansion which functions to slow down the bullet, maximize wound volume, and greatly reduce penetration. If the cavity of the conventional hollow-point bullet is filled with barrier material before it reaches its target, the bullet will tend to over-penetrate and frequently pass entirely through the target, thereby minimizing its desired effectiveness and endangering unintended targets.
In December of 1988, the Federal Bureau of Investigation Firearms Training Unit designed and implemented a special test protocol for evaluating effectiveness of modem ammunition, using various types of bullets. Each cartridge and bullet type submitted for testing was used in eight (8) different test events. All of the tests ultimately entailed the penetration of blocks of 10% ballistic gelatin, with or without intermediate barriers in front of the gelatin. These tests included firing bullets into bare gelatin at a distance of ten (10) feet, and through the following materials placed in front of the gelatin: heavy clothing, sheet steel, wall board (gypsum board), plywood and automobile glass. Tests were also conducted with heavy clothing at twenty (20) yards, and automobile glass at twenty (20) yards.
The Federal Bureau of Investigation (FBI) does not have a specific requirement for bullet expansion; however, the extent of bullet penetration is a closely controlled parameter. The FBI desires ammunition that penetrates at least 12 inches in 10% ballistic gelatin while not penetrating more than 18 inches. This depth of bullet penetration is desired regardless of what intermediate barriers are encountered by the bullet.
The FBI protocol is the most stringent test protocol ever devised for bullets. Many of the ammunition manufacturers soon discovered that the hollow-point bullets, which they had at that time, produced very poor results in 10% ballistic gelatin after passing through barriers. Even today, many of the best hollow-point bullets available perform only marginally well when tested using the FBI protocol.
Since the establishment of the FBI special testing protocol, the International Wound Ballistics Association (IWBA) has carried out further work. The IWBA has defined what it believes to be the ideal performance for bullets used for personal defense and law enforcement.
The IWBA has stated that, unlike the FBI, only two (2) terminal performance tests are necessary for evaluating ammunition. These two (2) tests are the bare gelatin test (identical to the FBI testing protocol), and an additional test consisting of shooting through four (4) layers of denim, continuing into a block of calibrated 10% ordnance gelatin. The IWBA has specified that terminal ballistics penetration in the bare gelatin should have a mean value of no less than 13 inches and no more than 14.0 inches. Further, the IWBA specifies that mean penetration in gelatin after passing through four (4) layers of denim should be no less than 12.5 inches and no more than 16.0 inches. In general, the IWBA requirement can be said to be within the range of 12.5-16 inches of penetration.
The four (4) layer denim test is an especially difficult test for current handgun ammunition. The denim will retard the expansion of most bullets by plugging the hollow-point cavity. This results in an unexpanded bullet. Such a bullet will over-penetrate its target, thereby threatening unintended targets and also failing to maximize the damage to the intended target. Many police departments have adopted the standards set by the IWBA, and much effort has been expended by ammunition manufacturers to create bullets that meet the IWBA""s ideal performance specifications.
Yet another standard for bullet performance has been established by the Immigration and Naturalization Service (INS). The INS has set a standard minimum depth of penetration at 9 inches in base gelatin. This reduced standard of penetration can be achieved with a bullet that expands to a greater extent, therefore slowing the bullet more and reducing the penetration to near nine (9) inches.
The design of our bullet is characterized by a series of elements which enable the bullet to expand after passing through intermediate barriers. These elements also allow the bullet to penetrate to the ideal depth of 12-16 inches in bare gelatin or minimum of 9 inches of penetration, depending on the standard used. While doing so, the bullet expands to between about 1.5-2.0 times its original diameter. It also retains near 100% of its weight.
Our preferred bullet is comprised of a jacket of malleable metal, such as one formed predominately of copper or copper alloy, and an inner core of lead or lead alloy. The bullet exterior is conventionally shaped. The front portion has a radiused or tapered open ended nose, and the rear portion has a rearward cylindrically shaped side wall.
The jacket encloses the lead core, except at the front-most portion which contains a hollow-point cavity in the core. The hollow-point cavity is conically shaped with an angle of 30-50 degrees, when measured from the axis of the bullet. Such an angle provides for a relatively shallow hollow-point cavity compared to conventional hollow-point bullets.
The prior art hollow point bullet has a relatively deep cavity in the nose which is defined by a straight cylindrically shaped wall which extends parallel to the longitudinal axis of the bullet. Often, the bottom of the cavity is conically shaped. The diameter of the mouth of the cavity is typically 0.50-0.70 times the diameter of the bullet.
The cavities in our hollow point bullets are of generally conical shape and the cavity-defining wall of each extends outwardly to the periphery at an angle of about 30-50 degrees to the longitudinal axis of the bullet. The larger the angle between the cavity wall and the longitudinal axis of this bullet, the more shallow will be the cavity, and the greater the tendency will be for the barrier material to slip radially outwardly therefrom, since the outward slope of the cavity wall will be more gentle. The smaller the angle, the steeper the slope will be toward the circumference of the bullet and the lesser the tendency will be for barrier material to slip radially outwardly. As the cavity wall approaches being parallel to the longitudinal axis of the bullet, the barrier material increasingly collects and remains within the cavity to a greater degree and tends to plug up the cavity, thereby increasingly blocking entrance of viscous material into the cavity and consequently minimizing expansion of the bullet.
The configuration of the hollow-point cavity serves two (2) purposes. First, it prevents clogging of the hollow-point cavity by allowing at least a portion of any picked-up barrier material to be wiped away by the target material as the bullet enters the target. This enables expansion after passing through the barrier material and entering the target, because it permits the cavity to receive and retain viscous materials readily available throughout the body of the target. Conventional hollow-points, having deep and nearly straight-walled cavities extending substantially parallel to the longitudinal axis of the jacket, become plugged with barrier materials which minimizes the amount of viscous material which may enter the cavity and thereby prevents adequate expansion. Secondly, the shape of our hollow-point cavity provides for a low thickness of lead and copper between the hollow-point cavity and exterior of the bullet. It appears that reducing the thickness of this area will reduce the amount of hydraulic pressure needed in the hollow-point cavity to induce expansion.
The nose portion of our jacket has a number of equally spaced deep scores which extend from the leading edge rearwardly and generally parallel to the longitudinal axis of the bullet, to an optimum length determined by terminal testing. The external scoring of the jacket allows the jacket to be deformed by hydraulic pressure within the hollow-point cavity, with a minimum of force. Such a force is readily generated by the liquid or flesh of the target, because the cavity of the hollow-point will be relatively free of barrier material.
A further element which reduces the amount of hydraulic force necessary to expand the bullet is preforming of the lead core. The forward or leading portion of the lead core is formed into multiple, physically separated, equally spaced segments or wedges, the sides of which extend from the bullet center in a radial direction perpendicular to the longitudinal axis of the bullet, as shown in FIG. 7. The wedge-shaped core segments are swaged together and comprise the forward end portions of the lead core. They extend from the hollow-point cavity in the front end to a point near the longitudinal middle of the bullet. The length of the segmental sections are optimized so that the bullet expands at and after it enters its target to a diameter which results in an optimum penetration depth in bare gelatin of 12.5-16 inches, which is the preferred depth of penetration according to FBI and IWBA standards, or a minimum of nine (9) inches for INS standards.
The preforming of the lead into wedge-shaped segments weakens the lead core in the front portion of the bullet. The weakening of the core reduces the amount of hydraulic pressure needed to expand the bullet. The physically separated wedge-shaped segments, when swaged into the tapered nose portion of the bullet, retain at least some of their individualized characteristics, so that they will readily separate when the subsequent substantial expansion takes place as the bullet moves along within the target, to the depth of 12.5-16 inches. Our bullet, which requires less hydraulic pressure to expand, will penetrate through difficult intermediate barriers, yet still expand when a conventional bullet will not.
Our bullet""s copper jacket has a different thickness throughout its length from front to rear. The jacket is relatively thin at its front end near the mouth of the hollow cavity, to readily sever, and thereby facilitate early expansion. This provides the thin hoop of material around the nose which readily severs, as referred to above. The jacket tapers toward its cylindrical wall to over double the thickness of the jacket material at the mouth of the tapered portion of the jacket. The weakened elements of the jacket construction causes the jacket to be sufficiently weak to encourage expansion and to be sufficiently strong after penetration of the target, to ensure structural integrity and weight retention. A conventional bullet which expands easily, is in danger of over-expansion and weight loss, the latter due to pieces of the bullet breaking off while expanding.
While moving within the target, each of the petals of the jacket fold back along the body 10 of the bullet in an arc that supports a segment of the lead core which also expands outwardly from the hollow-point cavity. This results in each of the above segments resting upon a petal or panel of the jacket, which has been defined previously by deep scoring. These petals remain intact as part of the spent bullet, between the cylindrical portion of the jacket and the expanded segment of the lead core.
The construction of our jacket also provides improved performance after the bullet has passed through barrier material such as steel sheet metal (as used in the construction of automobile bodies). After passage through the steel barrier and upon entering the target, the bullet jacket and core bulge and expand. In our bullet the bulging of the core and jacket is to a higher degree than conventional hollow-point bullets, because of the freedom with which the segments can separate from each other, due to the retention of at least some of their individual body characteristics. The deep scoring of the jacket causes the petals to separate and does not prevent the lead core from expanding slightly. This increased expansion within the target provides for a larger wound profile and prevents over penetration of the target.
The above-described bullet will expand and penetrate in 10% ballistic gelatin to meet the ideal specifications set by the FBI and the IWBA of 12.5-16 inches of penetration in bare gelatin. The bullet provides the additional advantage of virtually 100% weight retention and expansion amounting to 1.5-2.0 times the original diameter of the bullet before being fired. This bullet will penetrate through intermediate barriers of wall board, plywood, heavy clothing and denim, to thereafter expand and penetrate to ideal parameters. The bullet will also provide improved performance through automobile sheet metal as described hereinbefore. If necessary to meet the alternative INS standard of 9 inches of penetration, the bullet core may be preformed with segments extending to a greater extent, so as to produce a greater expansion and consequent lesser penetration.